Use conf package for llvm

Author: smuenzel

packages/z3/z3.4.15.1/opam

@@ -5,9 +5,6 @@ homepage: "https://github.com/Z3prover/z3"
 bug-reports: "https://github.com/Z3prover/z3/issues"
 license: "MIT"
 dev-repo: "git+https://github.com/Z3prover/z3.git"
-depexts: [
-  ["llvm"] {os-distribution = "homebrew"}
-]
 patches: [
   "gccstd-2a.patch" { (os-family = "opensuse" | os-family = "suse") | (os-distribution = "ubuntu" & os-version <= "20.04") }
 ]
@@ -41,6 +38,7 @@ depends: [
   "ocaml" {>= "4.08.0"}
   "ocamlfind" {build}
   "zarith"
+  "conf-llvm" { os-distribution = "homebrew" }
   "conf-python-3" {build}
   "conf-c++" {build}
 ]